The present invention relates generally to the field of integrated circuit test systems and, more particularly, to electromigration test systems and methods for using electromigration test systems.
Electromigration (EM) is the transport of material caused by the gradual movement of metal atoms in a conductor due to the transfer of momentum between conducting electrons and the metal atoms. Electromigration-induced voids nucleate when metallic ions are dislodged from the crystal lattice of the conductor. Voids can grow, migrate, and agglomerate. Electromigration can also induce extrusion in regions where metal atoms agglomerate. Void agglomeration and extrusion generally occur at opposite ends of a conductive member. Voids generally agglomerate near an electron source, and extrusion generally occurs near an electron drain. Electromigration can have negative effects, such as decreasing the reliability of integrated circuits. Integrated circuits can fail due to electromigration when voids grow or agglomerate and break interconnects and/or when electromigration-induced extrusion causes a short circuit.
A typical electromigration test system passes a current through an interconnect and measures resistance as a function of time in order to detect electromigration. Voids generally nucleate at defective sites in the interconnect crystal lattice. Void growth and agglomeration reduces the local cross-sectional area of the interconnect over time, and the resistance of the interconnect increases as a result.